The present invention relates generally to the field of electrolysis and, more particularly, to the separation of water into its elemental components via electrical current.
Our world has been running on fossil fuels (coal and petroleum) for over two hundred years, and is fast using these fuels up. Since it takes millions of years for these fuels to form, the need for an alternate source of energy is growing more and more urgent. The burning of fossil fuels has also been a major contributor to pollution and a possible cause of global warming.
Wind, water, geothermal and tidal energy sources have all been developed but they are limited to specific places. Fission has been developed as well, but has met sturdy resistance from environmental action groups. Fusion energy has yet to live up to its promise. Solar energy via photovoltaic cells has also been developed but these use less than 15% of the available energy and are not yet cost efficient.
Fuel cells, which produce energy by recombining oxygen and hydrogen to generate electricity, have reached 70 to 80 percent efficiency and, since they produce only water, are non-polluting and do not contribute to the greenhouse effect. Until now, the main source of hydrogen for such systems has been through the electrolysis of water. Because energy is required for the electrolysis process, and because in any system some energy is lost to entropy, this process has been inefficient. Many elaborate methods have been designed to reduce the amount of energy needed to split water. Because these either have not worked, or have been very expensive or inefficient processes, it has not been practical to scale up any of these methods for commercial use.
It has been known for over 100 years that hydrogen and oxygen gas may be generated by the electrolysis of water. Electrolysis utilizes electrical power to create a current between an anode and cathode, thereby breaking water into its constituent components, hydrogen and oxygen. Of course, this process has the potential to be particularly important in view of the concern associated with access to hydrocarbons in politically unstable countries. As is well known to those skilled in the art, hydrogen is a clean, plentiful and readily usable fuel. Needless to say, an efficient and economical method of producing hydrogen from readily available materials such as water could have significant value, especially in countries that have few hydrocarbon deposits. Consequently, there is a growing interest in developing new techniques for the efficient production of molecular hydrogen.
In order to reduce the amount of electrical energy necessary to sunder the hydrogen-oxygen bond in water, solar energy is being explored as an energy source. One approach which has been actively explored involves chemical processes which resemble photosynthesis in order to convert water and air into combustible hydrocarbons. Another approach, which is the approach taken by the instant invention, is to accomplish production of hydrogen gas by using sunlight to effect electrolysis of water. Generally, the emphasis with electrolysis has been to use some type of exotic solid state photoelectric cell to generate current and release hydrogen and oxygen. To date, the solid state photoelectric approaches have not proven economically successful.
In 1905, Albert Einstein explained the photoelectric effect using the quantum hypothesis. The photoelectric effect involves the ejection of electrons from a metal surface by light in a vacuum tube. Einstein developed the equation for the energy of these electrons in 1906. The equation is:
E=h"ugr"xe2x88x92W
This equation means that the energy (E) of the electrons is equal to Plank""s constant (h), multiplied by the frequency of the light ("ugr"), minus the work function (W) of the metal.
For the energy of the electrons to equal that needed for the electrolysis of water, the frequency of light must be in the range of high frequency ultraviolet. Thus, solar energy has heretofore had only limited use in producing hydrogen.
Thus, there exists a need for a method and apparatus that provides efficient electrolysis of water into its constituent elements. Accordingly, it should now be recognized, as was recognized by the present inventors, that there exists, and has existed for some time, a very real need for an invention that would address and solve the above-described problems.
Before proceeding to a description of the present invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be construed as limiting the invention to the examples (or preferred embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of this invention within the ambit of the appended claims.
This instant invention provides an efficient method of performing electrolysis on water, thereby separating it into its elemental components. More specifically, according to a preferred aspect of the instant invention, there is provided an apparatus and method for splitting water into hydrogen and oxygen. The inventive apparatus and method employ a specially prepared cathode in conjunction with incident light energy to increase the efficiency of that process.
According to a first preferred embodiment, there is provided an electrolysis apparatus wherein the cathode serves both as a photon collector and as an electrode for electrolysis. Of particular importance for purposes of the instant invention is the fact that the photon collector/cathode consists of a thin layer of metal, preferably nickel, deposited by electroplating or some similar technique (e.g., vapor deposition) onto a conductive surface (e.g., a sheet of copper metal). The electroplating produces a xe2x80x9cblackedxe2x80x9d (i.e., black or nearly black or otherwise darkened) surface which appears to be a microcrystalline deposit of metal. This metal xe2x80x9cblackxe2x80x9d serves both to collect and absorb the light and simultaneously acts as a cathodic surface for the electrolysis of water. The material and structure (i.e., the way that the surface metal is deposited) affect the efficiency of the photo-assisted electrolysis and operate to capture energy over a much larger portion of the solar spectrum.
In operation, the anode and specially prepared cathode are preferably immersed in a solution comprising an electrolyte along with the material (e.g., water, acetic acid, or other organic or inorganic compound) that is to be electrolyzed. An electrical potential is then created between the anode and the specially prepared cathode, and the cathode is irradiated with light. Light incident upon the cathode contributes additional energy to the electrolysis process, thereby reducing the amount of electricity necessary to separate a given quantity of water molecules. Of course, in the preferred embodiment, the incident light will be solar light, although many other light sources might be used. However, solar light sources have the advantage of providing photons to the reaction at no xe2x80x9ccostxe2x80x9d, in contrast to artificial light sources which must be supplied with power, thereby reducing the overall efficiency of the process.
Although light has previously been used to assist in the electrolysis process, such prior usage has occurred within much more complex systems of semiconductors and/or metal ions complexed in organic compounds. Thus, the principle advantage of the instant apparatus and method is that the inventive system operates simply and efficiently to reduce the electrical energy required for electrolysis.
Since much less energy is needed to produce hydrogen using the inventive system, fuels cells can now be run on hydrogen gas (H2) that is produced much efficiently and cost effectively, thus providing commercial viability. In addition, the inventive method of producing hydrogen gas does not threaten the environment as do fossil and nuclear energy sources.
The inventive system can be employed at any level or scale, from individual cell phones to power plants. Because the process uses inexpensive, readily available materials, it could be used in third world countries, as well as in the earth""s most technologically advanced countries. Furthermore, because energy and water are the only products of this process, the problem of pollution has been eliminated.
In addition to hydrogen production, the inventive apparatus and method can also be used in other electrochemical processes. For example, certain organic acids have been shown to decarbonylate and break down under certain electrolysis conditions to methane, ethane and carbon dioxide. This invention can be used to remove or reduce such acids in waste streams through solar assisted electrolysis. A number of similar electrochemical reactions where this invention could be used are known in both organic and inorganic chemistry.
The foregoing has outlined in broad terms the more important features of the invention disclosed herein so that the detailed description that follows may be more clearly understood, and so that the contribution of the instant inventors to the art may be better appreciated. The instant invention is not to be limited in its application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. Rather, the invention is capable of other embodiments and of being practiced and carried out in various other ways not specifically enumerated herein. Finally, it should be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting, unless the specification specifically so limits the invention.